Studies of short-time and high-temperature annealing and magnetic property of LaFe11.4Si1.6 compound

The LaFe11.4Si1.6 compounds are prepared by arc-melting and then annealed at different high temperatures from 1323 K (5 h) to 1623 K (2 h). The powder X-ray diffraction (XRD) and microstructure observations show that large amount of 1:13 phase begins to appear in the LaFe11.4Si1.6 compound annealed at 1423 K (5 h). In the temperature range from 1423 K to 1523 K, the alpha-Fe and LaFeSi phases rapidly decrease to form 1:13 phase. The LaFeSi phase is rarely observed by XRD when the as-cast compound is annealed at 1523 K (5 h). With annealing temperature increasing to 1573 K, LaFeSi phase is detected again in LaFe11.4Si1.6 compound. In LaFe11.4Si1.6 compounds annealed at 1523 K (5 h. at 1373 K (2 h)+1523 K (5 h), and 1523 K (7 h)+1373 K (2 h), the impurity phases including small amount of alpha-Fe and LaFeSi phase reduce in turn. The magnetic measurement shows that LaFe11.4Si1.6 compounds annealed by above three processes keep the first-order of magnetic transition behavior, and T-C are both at about 200 K. But the values of the maximal Delta S-M(T, H) of has large difference, they are 9.94, 12.66, and 13.96 J/(kg.K) under a magnetic field of 0-2 T, respectively.